The present invention relates generally to a digital audio disc transport device capable of reading digitally encoded information from compact discs (CDs), and in particular, to a disc transport device incorporating cue and shuttle searching and which is capable of muting the digital audio output during various search procedures.
CD transports (commonly referred to as CD players) in their short history have come to dominate the audio field. The compact disc contains between 2.sup.14 and 2.sup.15 grooves of digitally encoded information. Most of this digitally encoded information contains digital audio data which is converted from the digital format to an analog format toward being made audible to the listener. However, the digitally encoded information also contains track-start codes, indexing codes, disc identification codes, and various audio control information indicating, for example, that deemphasis is required.
CD transports receive the compact disc on a platform which positions the compact disc within the transport housing, such that it can be read by a moving CD optical pickup. The CD optical pickup scans the CD tracks for the digitally encoded information, which it feeds out in a serial data streams of audio and control information. The platform, CD pickup and rotating motor are all part of what is termed the "CD engine" found in all compact disc transports.
Compact discs are divided into a number of digitally encoded tracks each generally containing a single piece of music or "song". A track-code serves to divide or separate adjacent tracks from one another. Some compact disc manufacturers further divide these tracks into smaller units, termed indexes, to permit the user to select a particular pre-defined position from within a given track. Typical CD transports utilize the track-start codes to permit the user to switch, either forward or backward, from track-to-track. Some CD transports allow the user to select a particular index within a given track. However, because most compact disc manufacturers do not encode index codes onto the disc, a CD transport which incorporates an index search function is, nevertheless, unable to perform an index search.
In addition, most CD transports not only permit the user to move from track-to-track or index-to-index, but also permit the user to search in either fast-forward or rewind mode while still in the "play" mode, as might be desirable when searching for a particular passage within the music track. While performing such a search the listener will typically hear the music play at a faster rate while searching forward or backward, termed "intra-track scanning".
The typical prior-art CD transport device permits the user to perform track-to-track searching, index searching and intra-track scanning by typically providing momentary contact switches for the user to depress. Typically, the longer a switch is depressed the faster a search, index or scan is performed. An apparent limitation of such a control mechanism is the inherent lack of precision in the control offered, which is most severely noticed when attempting to perform intra-track scanning toward attempting to locate a specific point or passage within a given track or song. The user is often forced to repeatedly depress the control button often "over-shooting" the desired point or passage.
Those CD transports which do provide for intra-track scanning generally allow the digital audio data to continually stream out to the connected amplifier. Because of the increased speed with which the data is flowing, numerous "clicks" and "pops" are generated, which are unpleasant to the ear and potentially damaging to audio components to which the CD transport is connected.
Accordingly, one of the objects of the present invention is to permit the user to easily locate a desired point within a given track without having to repeatedly depress control buttons.
A further object of the present invention is mute the digital audio output signal when searching, indexing and scanning is performed toward minimizing the audibility and potential for damage caused by extraneous clicks and pops which occur during such searching, indexing, and scanning.
These objects, along with other objects, will become apparent in light of the present specification and drawings.